Conventional exhaust dyeing processes use water as the medium in which the dye is transported to the material being dyed.
Many processes have been described in which the dye bath comprises a non-aqueous organic solvent. These baths frequently utilize a volatile organic solvent, for example, perchloroethylene. Although perchloroethylene provides a good medium for dyeing, closed or pressurized machinery is often required to prevent loss of solvent and to reach the temperature range, required for dyeing.
A continuous process for waterless dyeing of textile and plastic materials, employing high boiling solvents, has been proposed by Hermes in U.S. Pat. Nos. 4,047,889 and 4,055,971. The vehicle recited is a high boiling glycol or glycol ether.
Another process, disclosed in allowed U.S. application, Ser. Nos. 440,567 and 440,611, filed Nov. 10, 1982, abandoned in favor of application Ser. Nos. 574,953 and 574,952, filed Jan. 30, 1984, utilizes as the principal dyeing medium a stable high boiling ester or ester mixture. Because of the stability and low volatility of the composition, dyeings can be carried out under atmospheric pressure at temperatures as low as 160.degree. C., typically 180.degree.-190.degree. C. The conditions disclosed by these applications, incorporated herein by reference, are eminently suited for the dyeing of polyester fibers with disperse dyes during very short dyeing cycles, frequently less than one minute.
Conventional disperse dyes normally contain water-soluble dispersing agents, and are generally unsuitable for use in non-aqueous solvent-based dyeing systems. Pure disperse dyes, without additives to aid dispersion or dissolution in the dyebath, are normally difficult to wet out and incorporate into the dye bath. Pure disperse dye means dye as manufactured and is typified, for example, by dried press-cake. Disperse dyes in this form may also suffer from batch-to-batch variation in strength and hue; such dyes are accordingly commercially unacceptable, without provision for standardization.
It is accordingly the object of this invention to provide a commercially-acceptable disperse dye concentrate of consistent strength and hue.